The way that this problem is normally solved is by adding a standard
icebox 12 volt conversion unit in the existing refrigerator. There are
several manufacturers that have thin plate evaporator coils that will
fit the rear wall of existing refrigerators. In the new Boat Works
magazine there is a article of a similar conversion to a 110 volt
refrigerator.

Storing energy in cold packs will not cool the box to refrigerator
temperatures.

From the author of four books on boat refrigeration
For a slide show on boat refrigeration go to;
http://www.kollmann-marine.com





Terry Spragg wrote in message t.cable.rogers.com...
wrote:
I have a large refrigerator and don't want to get rid of it since I'm
on the boat a lot, and the majority of the time at the dock. But do
like to go out for a couple of days each week, and the biggest
issue is the frig getting too warm unless the generator runs more
than I like it to. Do they make good cold packs of some kind that
can be frozen and re-frozen, and would help keep it colder without
so much use of the generator?

Like big blocks of home made ice? Phase change chemical salt "cold
packs" could offer some similar assistance.

Keep the door closed. Only more insulation can really help you.
Insulate especially between the compressor, radiator and the cold
chest, possibly increasing the insulated space between them by
extending the refrigerant lines.

Have you considered the technology of CO2 (dry) ice, or liquid
nitrogen? You could pump up a few gallons of Ln2 for use while the
engine is not used, etc. Well insulated dewars can keep Ln2 in
storage for some time, but the engine must still produce the energy
to produce this cold storage heat sink.

Some will say that using much dry ice may poison occupants during
sleep. Ln2 could displace O2, but not so likely as CO2, depending on
equipment failures.

Ln2 is relatively lightweight, and can be stored in floatation
space, ie. forepeak, etc. Piped into the freezer under the control
of a cryogenic thermostat, it could keep the contents cool, and
could possibly be "recharged" by the addition of more liquid
nitrogen, poured from a transport dewar to operational dewar aboard
the boat. It is a form of phase change heat energy storage system,
where it's evaporation provides a considerable heat sink.

Liquid nitrogen is not scarce, only a little obscure. Food
processing plants make and use a lot of it. 5 gallons of it would
likely keep your fridge cold for weeks, if it was well insulated and
kept closed.

I do nnot know how common small Ln2 compressor are, or how available.

Liquid N2 boils and evaporates while in the dewar, dependant on it's
insulation efficiency. What comes off of the stored container is
very cold nitrogen gas. Cast off evaporated N2, still cold, could be
used to augment other air conditioning (refridgeration) systems.

I suppose this would be considered radical tech.

Terry k